As a part of a continuing series of studies on the delayed effects of ionizing irradiation of the brain of the monkey, the current effort includes sequential observations after whole brain exposure to 6000 rads of supervoltage radiation, in divided doses over a six-week period. The protocol simulates as closely as possible that used by twelve medical centers in therapy of malignant gliomas in humans. BIBLIOGRAPHIC REFERENCES: Caveness, W.F.: Pathology of radiation damage to the normal brain of the monkey. Symposium on Modern Concepts in Brain Tumor Therapy, National Cancer Institute Monograph. 1977 (In press). Kemper, T.L., O'Neill, R.R., and Caveness, W.F.: Effects of single dose supervoltage whole brain radiation in the Macaca mulatta. J. Neuropathol. Exp. Neurol. 1977 (In press)